This invention relates to a sleeve valve of the in-line type. More particularly, one aspect of the invention relates to such valves having a velocity guide wherein the invention is directed to a means for rapidly equalizing the pressure across the velocity guide upon initially opening the valve. Another aspect of the invention is directed to an improved drive assembly for such a valve providing easy assembly and disassembly of the valve.
In-line sleeve valves having velocity guides and drive assemblies are old in the art. Such a valve has an inlet and an outlet aligned generally along the same axis. A sleeve is mounted to a housing such that the longitudinal axis of the sleeve is generally aligned with the valve inlet axis. The sleeve has nozzles in its cylindrical wall, the nozzles being in a pattern extending substantially entirely around the cylindrical wall and over a selected length thereof. The size, shape and spacing of the nozzles are not material to this patent. A sleeve gate is slidably mounted to the sleeve and extends around the outer surface of the sleeve in sliding sealing engagement therewith. A drive assembly drives the sleeve gate between a closed position whereby the gate fully covers the nozzles to prevent the flow of fluid through the valve, and an open position whereby a selected length of the nozzle pattern is exposed to allow the maximum flow of fluid through the valve.
Such prior art in-line sleeve valves also include a velocity guide mounted to the sleeve gate and movable therewith. The velocity guide comprises a ring shaped as a conical section, the ring being located forward of the sleeve gate with the end of the largest ring diameter being forward of the end of smallest ring diameter. The purpose of the velocity guide is to maintain a constant fluid velocity at the entrance to all the exposed nozzles, by reducing the annular flow area perpendicular to the conical face of the velocity guide, to match the reduced volume of flow along the velocity guide in front of the nozzles. By maintaining a constant flow velocity over the exposed length of the nozzle pattern, velocity head loss in the annular cavity in front of the nozzles is significantly reduced, and all operating limitations, such as back pressure requirements, are removed. There is no limiting sigma value (cavitation index), and under any choked flow there is only a 15% loss in efficiency.
The prior art velocity guide has holes through the guide ring for the purpose of providing some equalization of the pressure across the velocity guide upon initially opening the valve. When the valve is fully closed, there is no pressure drop across the velocity guide, but when the valve begins to open, there is a sharp pressure drop created across the velocity guide. The purpose of the holes in the guide ring is to allow equalized pressure behind the guide, through the holes, thereby reducing the pressure drop across the guide ring under flowing conditions. However, it has been found that the holes in the ring are not sufficient to reduce the pressure drop as rapidly as desirable with the result that structural failure occurs in the velocity guide. All of this is prior art. The present invention overcomes these problems.
It is also known in the prior art to provide such an in-line sleeve valve with a drive assembly having upper and lower drive arms whereby the lower drive arms are pivotally mounted at their upper ends to the valve housing for rotation about an axis to provide swinging movement of the drive arms about that axis. Slide blocks are located at the lower ends of the arms. The valve sleeve gate has groove means in the outer surface of its side wall for receiving the slide blocks for sliding movement of the slide blocks in the groove means. The slide blocks engage the sleeve gate to slide the sleeve gate fore and aft between closed and fully open positions upon swinging movement of the drive arms. In accordance with the prior art valve of this type, each slide block is mounted to the lower end of a drive arm by a drive pin having a portion rotatably mounted in an opening in the slide block, and another portion press fit in an opening in the lower end of the drive arm. This mounting arrangement makes it difficult to assemble the valve, particularly where the valve is a large size. Typically, such valves range in size from 12 inches in diameter to 72 inches in diameter and larger. Assembly of these valves, particularly the larger ones, is difficult and even dangerous because of having to mount the valve sleeve to the housing while at the same time attempting to align the valve blocks in the sleeve gate grooves with the slide blocks, drive arms, and drive pins previously assembled. These problems are overcome by the improved mounting assembly of the present invention.
It is also known in the prior art to operate an in-line sleeve valve of the type to which this invention is directed by producing swinging movement of upper and lower drive arms in response to reciprocation of an actuator piston. The upper drive arms are rotatably mounted to opposite ends of a drive bar which in turn is mounted for reciprocating movement along an arcuate path. A bearing pin mount is provided for mounting the drive bar to the reciprocating piston so the drive bar moves fore and aft with the piston but is allowed to move vertically relative to the piston to accommodate its arcuate movement. Heretofore, the pin mount for mounting the drive bar to the piston included a pin having a threaded end that engaged a threaded hole in the piston. Such an arrangement has produced some difficulty in assembly. The present invention overcomes this problem.